When a 3-dimensional figure is designed, using a piece of software such as a CAD or the like, it is impossible to specify an optional point of coordinates in a 3-dimensional space on a 2-dimensional display by manipulating a pointing device such as a mouse or the like. In order to specify an optional point of coordinates in the 3-dimensional space, it is necessary to input values (x, y, z) of a set of coordinates, but an input manipulation is troublesome, and thus a processing is inefficient.
In relation to the aforesaid matter, Patent Document 1 discloses a technique for specifying an optional point in a 3-dimensional space. The technique disclosed Patent Document 1 is directed to 3-dimensional coordinate value inputting method of inputting designation of a position in a 3-dimensional space on a manipulation screen displayed as a 2-dimensional plane. In this method, a flat plane, which is parallel to a X-Y plane, is defined by fixing a value of Z, and is designated as an input-allowable extent, and a flat plane indicating the input-allowable extent is displayed. For example, when a cursor is vertically moved on a 2-dimensional screen, this movement is interpreted as a movement on the aforesaid flat plane, and the cursor is regulated to be moved only on the flat plane by decomposing a vector of the movement into an X component and a Y component. Then, a piece of positional information is input in a direction, which is not fixed, and is acquired as a set of 2-dimensional coordinates which defines a position on the screen. Thus, an X coordinate value and a Y coordinate value of the 3-dimensional coordinates on the aforesaid flat plane are found from the set of 2-dimensional coordinates.